Critical Power and W′ calculator
Enter 2 to 4 maximal efforts lasting between 3 and 20 minutes. The calculator runs a linear regression of P against 1/t: the slope is W′, the intercept is CP.
Your tests
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Critical Power
275 W
3.93 W/kg
W′
15.6 kJ
222 J/kg
Fit quality
R² = 0.993
Excellent fit
Your tests describe a clean line: the estimate is trustworthy.
Estimated FTP for zones
259 W≈ 94% of CP
Power-duration curve
The curve shows predicted maximal power for each duration. The dashed line is CP: the asymptote the curve falls towards.
Predicted maximal power
| 3 min | 361 W | 5.16 W/kg |
|---|---|---|
| 5 min | 327 W | 4.67 W/kg |
| 8 min | 307 W | 4.39 W/kg |
| 12 min | 297 W | 4.24 W/kg |
| 20 min | 288 W | 4.11 W/kg |
| 30 min | 284 W | 4.05 W/kg |
Training zones
calculated on estimated FTP, not on CP
- Z1Active recovery< 142 W
- Z2Endurance145 – 194 W
- Z3Tempo197 – 233 W
- Z4Threshold235 – 271 W
- Z5V̇O2max274 – 310 W
- Z6Anaerobic capacity313 – 388 W
- Z7Neuromuscular> 390 W